Optimization of Post-transplantation Benadamustine and Cyclophosphamide in Patients With High-risk Myeloid Malignancies and a Partially Mismatched Donor

This study is looking at the best doses of two medications — bendamustine and cyclophosphamide — given after a stem cell transplant from a partially matched donor, to help prevent the immune system from rejecting the transplant in people with high-risk blood cancers. **You may be eligible if...** - You need a bone marrow or stem cell transplant for a blood cancer - Your donor is a partial (not fully identical) genetic match — specifically matched on 5 key immune system markers but not a full 10/10 match - Your cancer includes acute myeloid leukemia (AML), chronic myeloid leukemia (CML), myelodysplastic syndrome (MDS), or other high-risk blood cancers - Your cancer is considered high-risk (e.g., has not responded to previous treatment, or has certain high-risk genetic features) **You may NOT be eligible if...** - You have a fully matched donor available (10/10 HLA match) - Your blood cancer is not one of the types listed above - Your overall health does not allow you to tolerate a transplant Talk to your doctor to see if this trial is right for you.